<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>流式布局</title>
</head>
<style>
    body>*{
        width: 70%;
        height: auto;
        margin: 0 auto;
        margin-top: 20px;
        border: 2px solid orange;
        padding: 5px;
    }
    header{
        height: 50px;
    }
    section{
        height: 300px;
    }
    footer{
        height: 30px;
    }
    section>*{
        height: 100%;
        border: 2px solid orange;
        float: left;
    }
    aside{
        width: 25%;
    }
    article{
        width: 70%;
        margin-left: 1%;
    }
</style>
<body>
    <header>header</header>
    <nav>nav</nav>
    <section>
        <aside>aside</aside>
        <article>article</article>
    </section>
    <footer>footer</footer>
</body>
</html>